Lomefloxacin, a new fluoroquinolone: Studies on in vitro antimicrobial spectrum, potency, and development of resistance

Abstract

Lomefloxacin (NY-198; SC-47111), a potent new difluoroquinolone, was studied to compare its in vitro activity with that of other antimicrobials against 2194 clinical isolates. Lomefloxacin showed excellent inhibitory and bactericidal activity against strains of Enterobacteriaceae and inhibited greater than 99% of the isolates at a concentration of 4 μg/ml or less. Lomefloxacin exhibited good-to-moderate activity against strains of Acinetobacter (MIC 90 4μg/ml) and Pseudomonas aeruginosa (MIC 90 8 μg/ml), but poor activity for Pseudomonas cepacia (MIC 90 > 16 μg/ml). Staphylococcus aureus, and Staphylococcus epidermidis isolates, both oxacillin-susceptible and -resistant strains, were susceptible (MIC 90 1 μg/ml) to lomefloxacin and the other fluoroquinolones. Strains of Haemophilus influenzae, (MIC 90 ⩽0.13 μg/ml) Neisseria gonorrhoeae MIC 90 ⩽0.03 μg/ml), and Branhamella catarrhalis (MIC 90 ⩽0.03 μg/ml) were highly susceptible to lomefloxacin. Streptococcal isolates, especially viridans streptococci, were considerably less susceptible to the fluoroquinolones. Overall, lomefloxacin had comparable activity to norfloxacin, fleroxacin, and ofloxacin, and against many facultative anaerobes lomefloxacin was more active than imipenem, cefotaxime, ceftazidime, ticarcillin/clavulanic acid, aztreonam, trimethoprim/sulfamethoxazole and gentamicin. Development of resistance to lomefloxacin by spontaneous mutation was low and comparable to that of other fluoroquinolones. Growth in subinhibitory concentrations resulted in increased resistance to fluoroquinolones for selected test strains.